1. Field of the Invention
This invention relates to a radiation image recording, read-out and reproducing apparatus wherein read-out and reproduction of a radiation image are carried out by use of the same scanning system in the same apparatus, and at least one stimulable phosphor sheet is circulated and reused in the apparatus.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. Nos. 4,258,264, 4,276,473, 4,315,318 and 4,387,428 and Japanese Unexamined Publication Pat. No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then scanned with stimulating rays which cause it to emit light in proportion to the stored radiation energy. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to electric image signals, which are processed as desired to reproduce a visible image having an improved image quality, particularly a high diagnostic efficiency and accuracy. The visible image finally obtained may be reproduced in the form of a hard copy or may be displayed on a cathode ray tube (CRT). In this radiation image recording and reproducing system, the stimulable phosphor sheet is used to temporarily store the radiation image in order to reproduce the final visible image therefrom on a final recording medium. For economical reasons, therefore, it is desirable that the stimulable phosphor sheet be used repeatedly.
Further, in a mobile X-ray diagnostic station such as a traveling X-ray diagnostic station in the form of a vehicle like a bus which is provided with a radiation image recording and read-out apparatus for carrying out the aforesaid radiation image recording and reproducing system and moves from place to place to record radiation images for mass medical examinations, it is disadvantageous to load the mobile X-ray diagnostic station with a large number of stimulable phosphor sheets, and the number of the stimulable phosphor sheets which can be loaded on the mobile X-ray diagnostic station is limited. Therefore, it is desirable to load the mobile X-ray diagnostic station with stimulable phosphor sheets which can be used repeatedly, and circulate and reuse the stimulable phosphor sheets for further image recording and read-out operations, thereby obtaining the radiation image signals of many objects. Further, when image recording is carried out continuously by circulating and reusing the stimulable phosphor sheets, it becomes possible to increase the image recording speed in mass medical examination. This is very advantageous in practical use.
In order to reuse stimulable phosphor sheets as mentioned above, the radiation energy remaining on the stimulable phosphor sheet after it is scanned with stimulating rays to read out the radiation image stored thereon should be erased by a method as described in, for example, U.S. Pat. No. 4,400,619 or Japanese Unexamined Publication Pat. No. 56(1981)-12599. The stimulable phosphor sheet should then be used again for radiation image recording.
From the aforesaid viewpoint, the applicant proposed in Japanese Unexamined Publication Pat. No. 59(1984)-192240 a built-in type radiation image recording and read-out apparatus comprising:
(i) a circulation and conveyance means for conveying at least one stimulable phosphor sheet for recording a radiation image thereon along a predetermined circulation path, PA1 (ii) an image recording section disposed on the circulation path for recording a radiation image of an object on the stimulable phosphor sheet by exposing the stimulable phosphor sheet to a radiation passing through the object, PA1 (iii) an image read-out section disposed on the circulation path and provided with a stimulating ray source for emitting stimulating rays for scanning the stimulable phosphor sheet carrying the radiation image stored thereon at the image recording section, and a photoelectric read-out means for detecting light emitted by the stimulable phosphor sheet scanned with the stimulating rays to obtain electric image signals, and PA1 (iv) an erasing section disposed on the circulation path for, prior to the next image recording on the stimulable phosphor sheet for which the image read-out has been carried out at the image read-out section, having the stimulable phosphor sheet release the radiation energy remaining on the stimulable phosphor sheet, PA1 whereby the stimulable phosphor sheet is circulated through the image recording section, the image read-out section and the erasing section, and reused for radiation image recording. PA1 (i) a circulation and conveyance means for conveying at least one stimulable phosphor sheet along a predetermined circulation path, PA1 (ii) a recording sheet feeding section for housing recording sheets and feeding out said housed recording sheets one by one, PA1 (iii) an image recording section disposed on said circulation path for recording a radiation image on said stimulable phosphor sheet by exposing said stimulable phosphor sheet to a radiation carrying image information, PA1 (iv) a light beam scanning section disposed on said circulation path and provided with a read-out main scanning means for deflecting a light beam by a light deflector and scanning said light beam in a main scanning direction on said stimulable phosphor sheet, a reproducing main scanning means for deflecting a light beam by a light deflector and scanning said light beam in the main scanning direction on said recording sheet, and a sub-scanning means for scanning said stimulable phosphor sheet and said recording sheet respectively in a sub-scanning direction by moving them in the sub-scanning direction approximately normal to said main scanning direction, wherein read-out of said radiation image is carried out by causing said stimulable phosphor sheet to emit light carrying said radiation image by the light beam in said read-out main scanning means and detecting the emitted light by use of a light detection means, and reproduction of said radiation image on said recording sheet is carried out by modulating the light beam in said reproducing main scanning means in accordance with said radiation image thus read out, PA1 (v) an erasing section disposed on said circulation path for, prior to the next image recording on said stimulable phosphor sheet for which the image read-out has been carried out at said light beam scanning section, having said stimulable phosphor sheet release the radiation energy remaining on said stimulable phosphor sheet, and PA1 (vi) a recording sheet conveyance means for receiving said recording sheet fed out of said recording sheet feeding section, conveying said recording sheet to said light beam scanning section, and thereafter conveying said recording sheet out of said light beam scanning section in a direction different from the direction of conveyance of said circulation and conveyance means.
On the other hand, the image signals detected in the manner as mentioned above may be stored on a storage medium having a large storage capacity, such as a magnetic tape, and used for reproducing a visible image on a recording sheet or the like at a location remote from the built-in type apparatus, or may be used for reproducing a visible image on a recording sheet or the like immediately after the image read-out. In any case, in order to reproduce the radiation image, which was recorded on the stimulable phosphor sheet, on the recording sheet, it is necessary to provide a reproducing apparatus for scanning a light beam modulated in accordance with the detected image signals on the recording sheet. Therefore, in order to form the final visible image of the radiation image, which was stored on the stimulable phosphor sheet, on the recording sheet in the conventional radiation image recording and reproducing system, it is necessary to provide at least two independent apparatuses, i.e. the aforesaid built-in type apparatus and the reproducing apparatus.
In recent years, various attempts have been made to make the aforesaid radiation image recording and reproducing system as a whole smaller and to reduce the manufacturing cost of the system. However, with the conventional radiation image recording and reproducing system, the recording and read-out apparatus and the reproducing apparatus must be provided independently of each other as mentioned above, and the system as a whole cannot be made so small.
In particular, the built-in type apparatus is suitable for loading on a mobile X-ray diagnostic station such as a traveling X-ray diagnostic station in the form of a vehicle like a bus for the purpose of mass medical examinations or the like as mentioned above and should preferably be made as small as possible. However, in the case where a radiation image is to be reproduced into a visible image immediately after the radiation image is recorded and read out, the mobile X-ray diagnostic station must be loaded with both the recording and read-out apparatus and the reproducing apparatus, and therefore becomes larger as a whole. Also, a scanning system including a light source and other components must be provided independently in the image read-out section of the recording and read-out apparatus and the reproducing apparatus respectively and therefore the manufacturing cost of the radiation image recording and reproducing system cannot be reduced markedly.
Also, though an X-ray image read-out and reproducing apparatus wherein the same light source is utilized for read-out and reproduction, and read-out and reproduction are carried out alternately in the same stage is proposed in Japanese Unexamined Publication Pat. No. 58(1983)-184677, only a conceptual view of the apparatus is shown in the specification thereof and no concrete configuration of the apparatus is described therein. Therefore, it is not always possible to put such an apparatus into practical use. Also, with the proposed apparatus, scanning is carried out by moving the light source and a photodetector with respect to a sheet. With such a scanning method, the movement mechanism becomes complicated and it is not always possible to achieve quick scanning. Further, with the proposed apparatus wherein a light modulator and the photodetector are moved by a drive mechanism into and out of an optical path in the course of change-over of the apparatus between read-out and reproduction, the apparatus is also rendered complicated by the drive mechanism.